Our long-term goal is to gain a highly mechanistic understanding of how the actin cytoskeleton directs cell polarity and cell morphogenesis. All living cells have internal and external structures tailored to and critical for their distinctive physiological functions. Further, cell architecture can be changed rapidly in response to various cues. The mechanisms underlying these events remain poorly understood and represent a major challenge for cell biologists to define. Recently, a conserved family of proteins called formins has emerged as crucial regulators of actin assembly and remodeling in cells, often functioning directly downstream of Rho GTPases. Formins are large multi-domain proteins that play essential roles in cell polarity, cell division, cell migration, endocytosis, and cell adhesion in a wide range of organisms. Formins directly nucleate actin assembly by a novel mechanism and remain processively attached to the growing end of the filament, protecting the end from capping proteins while guiding insertion of new actin subunits. While the last five years have seen rapid progress in elucidating formin protein structure, mechanism and function, comparatively little is known about how formin activities are regulated spatially and temporally in cells. In this proposal, we will address this question using the budding yeast Saccharomyces cerevisiae as a model organism. Whereas mammals have 15 different formin genes, S. cerevisiae has only two (Bni1 and Bnr1), and hence offers a simplified model to dissect formin regulation. Yeast also allows us to take a multidisciplinary approach, combining genetics, biochemistry, and live cell imaging. Bni1 and Bnr1 have distinct localization and dynamics, and assemble two distinct sets of actin cables. These cables serve as polarized tracks required for targeted secretion and polarized cell growth. We will determine how one of these formins (Bnr1) is regulated in vivo, which will provide key mechanistic insights into the molecular basis of cell polarity and cell morphogenesis.
The Specific Aims of the proposal are: (1) How is Bnr1 anchored at the bud neck, activated/released from an autoinhibited state, and then retrieved from actin filament ends for new rounds of actin assembly? (2) How are the activities and cellular functions of a novel Bnr1-regulator (Bud14) controlled by its in vivo binding partners (Kel1 and Kel2)? Defining the molecular basis of these events is critical not only for understanding normal human cell biology and physiology, but also for determining how mutations in the genes encoding morphogenetic determinants give rise to disease states including cancer, birth defects, and neurodegenerative disorders.
| Garabedian, Mikael V; Stanishneva-Konovalova, Tatiana; Lou, Chenyu et al. (2018) Integrated control of formin-mediated actin assembly by a stationary inhibitor and a mobile activator. J Cell Biol 217:3512-3530 |
| Sokolova, Olga S; Chemeris, Angelina; Guo, Siyang et al. (2017) Structural Basis of Arp2/3 Complex Inhibition by GMF, Coronin, and Arpin. J Mol Biol 429:237-248 |
| Shekhar, Shashank (2017) Microfluidics-Assisted TIRF Imaging to Study Single Actin Filament Dynamics. Curr Protoc Cell Biol 77:12.13.1-12.13.24 |
| Henty-Ridilla, Jessica L; Juanes, M Angeles; Goode, Bruce L (2017) Profilin Directly Promotes Microtubule Growth through Residues Mutated in Amyotrophic Lateral Sclerosis. Curr Biol 27:3535-3543.e4 |
| Henty-Ridilla, Jessica L; Rankova, Aneliya; Eskin, Julian A et al. (2016) Accelerated actin filament polymerization from microtubule plus ends. Science 352:1004-9 |
| Alioto, Salvatore L; Garabedian, Mikael V; Bellavance, Danielle R et al. (2016) Tropomyosin and Profilin Cooperate to Promote Formin-Mediated Actin Nucleation and Drive Yeast Actin Cable Assembly. Curr Biol 26:3230-3237 |
| Mohapatra, Lishibanya; Goode, Bruce L; Jelenkovic, Predrag et al. (2016) Design Principles of Length Control of Cytoskeletal Structures. Annu Rev Biophys 45:85-116 |
| Eskin, Julian A; Rankova, Aneliya; Johnston, Adam B et al. (2016) Common formin-regulating sequences in Smy1 and Bud14 are required for the control of actin cable assembly in vivo. Mol Biol Cell 27:828-37 |
| Bombardier, Jeffrey P; Eskin, Julian A; Jaiswal, Richa et al. (2015) Single-molecule visualization of a formin-capping protein 'decision complex' at the actin filament barbed end. Nat Commun 6:8707 |
| Mohapatra, Lishibanya; Goode, Bruce L; Kondev, Jane (2015) Antenna Mechanism of Length Control of Actin Cables. PLoS Comput Biol 11:e1004160 |
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